Users of computer networks, such as corporate networks or the Internet, routinely send electronic messages to each other. Electronic messages may contain, for example, text, images, links, and attachments. Electronic mail or email is one of the most widely used methods of communication over the Internet due to the variety of data that may be transmitted, the large number of available recipients, speed, low cost and convenience.
Email messages may be sent, for example, between friends, family members or between coworkers thereby substituting for traditional letters and office correspondences in many cases. This is made possible because the Internet has very few restrictions on who may send emails, the number of emails that may be transmitted and who may receive the emails. The only real hurdle for sending emails is the requirement that the sender must know the email address (also called network mailbox) of the intended recipient.
Email messages travel across the Internet, typically passing from server to server, at amazing speeds achievable only by electronic data. The Internet provides the ability to send an email anywhere in the world, often in less than a few seconds. Delivery times are continually being reduced as the Internet's ability to transfer electronic data improves.
Most Internet users find emails to be much more convenient than traditional mail. Traditional mail requires stamps and envelopes to be purchased and a supply maintained, while emails do not require the costs and burden of maintaining a supply of associated products. Emails may also be sent with the click of a few buttons, while letters typically need to be transported to a physical location, such as a mail box, before being sent.
Once a computer and a network connection have been obtained, there are typically few additional costs associated with sending emails. This remains true even if millions, or more, of emails are sent by the same user. Emails thus have the extraordinary power of allowing a single user to send one or more messages to a very large number of people at an extremely low cost.
The Internet has become a very valuable tool for business and personal communications, information sharing, commerce, etc. However, some individuals have abused the Internet. Among such abuses are spam and phishing. Spam, or unsolicited email, is flooding the Internet with many copies of the identical or nearly identical message, in an attempt to force the message on people who would not otherwise choose to receive it. Most spam is commercial advertising, often for dubious products, get-rich-quick schemes, or financial or quasi-legal services.
A single spam message received by a user uses only a small amount of the user's email account's allotted disk space, requires relatively little time to delete and does little to obscure the messages desired by the user. Even a small number of spam messages, while still annoying, would nonetheless cause relatively few real problems. However, the amount of spam transmitted over the Internet is growing at an alarming rate. While a single or small number of spam messages are annoying, a large number of spam can fill a user's email account's allotted disk space thereby preventing the receipt of desired emails. Also, a large number of spam can take a significant amount of time to delete and can even obscure the presence of desired emails in the user's email account.
Spam messages currently comprise such a large portion of Internet communications that they actually cause data transmission problems for the Internet as a whole. Spam creates data log jams thereby slowing the delivery of more desired data through the Internet. The larger volume of data created by spam also requires the Internet providers to buy larger and more powerful, i.e. more expensive, equipment to handle the additional data flow caused by the spam.
Spam has a very poor response rate compared to other forms of advertisement. However, since almost all of the costs/problems for transmitting and receiving spam are absorbed by the recipient of the spam and the providers of the Internet infrastructure, spam nevertheless continues to be commercially viable for a spammer.
Phishing is the luring of sensitive information, such as passwords, credit card numbers, bank accounts and other personal information, from an Internet user by masquerading as someone trustworthy with a legitimate need for such information. Often phishing goes hand-in-hand with spam. The perpetrators send out a large number of email messages to lure as many people as they can to their phishing “nets”. Typically, if a user clicks on the link in the email, it would take the user to a webpage that appears very similar to a business that the user might trust. However, this webpage is controlled by the perpetrators and any information entered on the webpage will be forwarded to the perpetrators. The perpetrators may use users' information to commit fraud or other crimes. Often users' information is used for identity theft crimes.
If the user is able to see the URL address of the phishing webpage, the user may realize that it does not belong to a business that the user trusts. Phishers use various techniques to disguise their URL addresses. Among such techniques is hiding the true URL address in the phishing email behind some text, an address of a reputable business, or an image; removing the address bar in the Internet browser; replacing the address bar of the Internet browser with a fake address bar; using IP numbers instead of a domain name in the URL; using domain names that are similar in spelling to the domain names of the reputable businesses; using extremely long URL addresses that the beginning of the address would not be plainly visible in the address bar of the Internet browser; etc. Also, long URL addresses may be harder to analyze for the users, thus further helping the perpetrators in obscuring the true location of their phishing webpages.
There are various techniques used for combating spam and phishing. Among them are spam filtering, email challenge-response systems, maintaining white and/or black lists for email addresses, domain names, and IP (Internet Protocol) numbers, an Internet browser add-ons that show the true location of the pages viewed by the user, etc. Below are a few examples of such systems.
The SenderBase system keeps track of the amount of email messages originating from various domain names and IP addresses. IronPort Systems Inc., a company that maintains SenderBase.org, explains how it works in this example: “If a sender has high global volumes of mail—say 200 Million messages per day—from a network of 5 different domains and 1,700 IP addresses that have only been sending mail for 15 days yet have a high end user complaint rate and they don't accept incoming mail, they will have a very low reputation score [. . . ]. If a sender is a Fortune 500 company, they will likely have much more modest global email volumes—say 500,000 messages per day—will have a smaller number of IPs and domains with a long sending history, they will accept incoming email and have low (or zero) end user complaint rates.”
The Bonded Sender Program maintains a white list-like service. The participants of the service must adhere to the rules and post a bond to be included on the white list.
SpamCop maintains a black list of IP addresses and allows users to report spam to a centralized database.
Multiple solutions are created for establishing “societies” of trusted users. Some solutions keep track of user reputation or trust level.
Cloudmark, Inc. provides spam filtering and allows users to block or unblock messages manually. The users' votes on messages (blocking and unblocking) are reported to a centralized database, allowing for better spam filtering by reducing the number of false positives. Each Cloudmark user is assigned with a reputation (trust rating). If a malicious user unblocks a spam message, while a large number of other users block it, the malicious user's reputation will go down. If a user votes along the lines with the rest of the users, her/his reputation raises.
VeriSign, Inc. maintains the list of domain names that were issued a VeriSign SSL digital certificate, so called “Verified Domains List.” The company plans to make the list accessible to third parties.
Spoof Stick by CoreStreet Ltd. is an Internet browser add-on that displays the domain name or IP address of the page viewed by the user.
For many email filtering systems to work properly, the sender's email address or at least its domain name part should be correct. Often malicious users forge (spoof) the sender's email address when they send out spam, viruses, or phishing email messages. Among the proposals offered to address this problem are Microsoft's Sender ID and Yahoo's Domain Keys. The Sender ID proposal envisions publishing the sender's email IP addresses in the DNS records of the sender's server, thus allowing the receiver of the email message to compare the originating IP address in the email headers with the IP addresses published in the DNS. If they don't match, the email address was forged. The Domain Keys proposal utilizes public-private key infrastructure. The sender publishes its public key in the DNS records and digitally signs outgoing email messages with its private key. The receiver can validate the sender's signature using the sender's public key published in the DNS records. If the sender's signature cannot be validated, the sender's email address was forged.
Even though multiple systems are being used, the amount of spam, phishing, and other Internet abuses is steadily rising. The existing systems identify trust level of the email senders or analyze the content of the email message. However, an email sender may forge its true identity; an email sender may use a temporary email account; an email sender may use an open relay IP to send email messages; or an email sender may use somebody else's computer to send messages if virus or spy software was installed. Also senders of spam and phishing attacks may provide email message content that is not related to the content of the links embedded in the email or they may use content that looks absolutely legitimate. All of these make it very hard to keep track of email addresses and originating IP addresses, as well as filtering messages based on their content.
Therefore, new systems and methods are needed to overcome the limitations of the current systems and methods. It is desired to create systems and methods that provide more efficient solutions for combating Internet abuses, such as spam and phishing.